Image processing apparatus, image processing method, and program thereof

ABSTRACT

Disclosed herein is an image processing apparatus comprising: a read unit that reads a target to be read as color data of N colors (N is a positive integer) that form a color space; a generator that generates pixel data of one pixel from the read color data of the N colors; a determining unit that determines whether the generated pixel data is present in an achromatic edge area that includes an achromatic edge; and a processing unit that, if the generated pixel data is determined to be present in the achromatic edge area, generates, for pixels in the achromatic edge area, achromatic pixel data of the color space from one item of the read color data of the N colors forming the color space and also generates image data from the generated achromatic pixel data.

BACKGROUND

1. Technical Field

The present invention relates to an image processing apparatus, an imageprocessing method, and a program thereof.

2. Related Art

With a proposed image processing apparatus in related art, RGB dataundergoes IQ color difference conversion, and then color-monochromedetermination is conducted to detect a monochromatic pixel around apixel of interest. Depending on the result of this determination,whether the pixel of interest is a color shift pixel or a colored pixelis decided, and the colored pixel is examined again in consideration ofthe decision. Accordingly, a color shift at an edge of a black line iscorrected by considering a color shift caused by optical deviation andmechanical vibration of the image processing apparatus at the time ofinputting image data represented by RGB data and the like (see JapaneseUnexamined Patent Application Publication No. 2001-211334, for example).

SUMMARY

Although the apparatus described above can correct a color shift causedat an edge of a black line, the apparatus cannot increase the resolutionat the edge of this black line. A high resolution is desirable at blackline edges because they affect the visibility of, for example,characters.

An advantage of some aspects of the invention is to provide an imageprocessing apparatus and an image processing method that can achieve areduced color shift and an increased resolution in an achromatic area,as well as a program thereof.

According to an aspect of the invention, components described below areused to obtain the above advantage.

The image processing apparatus according to an aspect of the inventionhas a read unit that reads a target to be read as the color data of Ncolors (N is a positive integer) that form a color space, a generatorthat generates pixel data of one pixel from the read color data of the Ncolors, a determining unit that determines whether the generated pixeldata is present in an achromatic edge area that includes an achromaticedge, and a processing unit that, if the generated pixel data isdetermined to be present in the achromatic edge area, generates, for thepixels in the achromatic edge area, achromatic pixel data of the colorspace from one item of the read color data of the N colors forming thecolor space, and also generates image data from the generated achromaticpixel data.

This image processing apparatus reads the target to be read, which is aplurality of pixels, as the color data of N colors, and identifies anachromatic edge area that includes an achromatic edge in the read area.The image processing apparatus then uses one read color data item togenerate achromatic pixel data of the color space for the pixels in theidentified achromatic edge area, and also generates image data from thegenerated achromatic pixel data. A plurality of adjacent color dataitems, for example, may be used together to generate pixel data of onepixel. In this case, different color data items may be read fromdifferent positions, and thereby a color shift may occur from the colorof the target to be read. According to the aspect of the invention, inan achromatic edge area, one color data item that has been read is usedto generate achromatic pixel data in a color space, so a color shift isreduced. Since the one read color data item is the value of one pixel, ahigher resolution can be obtained than when, for example, a plurality ofcolor data items are handled together to take the value of one pixel.Accordingly, a reduced color shift and an increased resolution areachieved in an achromatic area.

The color space used may be an RGB color space, in which red (R), green(G), and blue (B) are used as primary colors. Alternatively, the colorspace may be a CMYK color space, in which cyan (C), magenta (M), andyellow (Y) are used as primary colors. In the RGB color space, colordata may be R values, G values, and the like, and achromatic pixel data(pixel data) may be RGB values. In the CMYK color space, color data maybe C values and M values, and achromatic pixel data (pixel data) may beCMYK values. To generate the achromatic pixel data, the processing unitmay use the one read color data item as a color data value for the Ncolors.

The processing unit in the image processing apparatus according to theaspect of the invention may generate pixel data of one pixel from thecolor data of N adjacent colors in the read color data. If the generatedpixel data is present in the achromatic edge area, the processing unitmay use the color data of N colors included in the pixel data, which hasbeen generated on the basis of the positions of the color data read bythe read unit, as the achromatic pixel data of N pixels to generate theimage data. Therefore, the resolution can be relatively easily increasedto N times by generating pixel data of one pixel from the N-color dataand then increasing the generated pixel data to N times.

The image processing apparatus according to the aspect of the inventionmay generate pixel data of one pixel from the color data of N adjacentcolors in the read color data, and may identify an achromatic edge areaon the basis of brightness information obtained from the generated pixeldata. Accordingly, the achromatic edge area can be easily identified andthe resolution can also be easily increased. In this case, to identifythe achromatic edge area, the image processing apparatus may determinewhether the pixel is achromatic on the basis of differences among colordata values included in the generated pixel data, and may identify theachromatic edge area by using a brightness value included in theobtained brightness information.

The processing unit in the image processing apparatus according to theaspect of the invention may also use the color data of the pixelsadjacent to a pixel in an area other than the achromatic edge area togenerate pixel data of the color space through an interpolation process,and may use the generated pixel data to generate image data.Accordingly, the resolution of the entire image data can be increased byuse of the interpolation process. Interpolation processes include, forexample, nearest neighbor interpolation, bilinear interpolation, andbicubic interpolation. When pixel data of one pixel is generated fromthe color data of adjacent N colors, the processing unit may also usethe color data of pixels adjacent to a pixel in other than theachromatic edge area to generate pixel data of N pixels through aninterpolation process, and may use the generated pixel data to generateimage data.

The read unit in the image processing apparatus according to the aspectof the invention may have opto-electric conversion devices, arranged ina main scanning direction, which opto-electrically convert lightobtained through the target to be read. The read unit may select a lightbeam, one at a time, from the N-color light beams constituting the colorspace and direct the selected light beam to the target. The read unitmay also move in a sub-scanning direction and read the target.Accordingly, in a case in which a target is read by selecting a color,one at a time, from N colors generated by opto-electric conversiondevices arranged in a main scanning direction and by moving theopto-electric conversion devices in a sub-scanning direction, theresolution can also be increased in the sub-scanning direction byincreasing the moving speed in the sub-scanning direction. Both a fastread speed and a high resolution are thereby achieved.

The image processing apparatus according to the aspect of the inventionmay have a printer that has an achromatic coloring agent and a chromaticcoloring agent, the achromatic coloring agent having a higher formingdensity on a print medium than the chromatic coloring agent. The imageprocessing apparatus may also have a print controller that controls theprinter so that the coloring agents are transferred to the print medium.The print controller may control the printer so that the coloring agentsare transferred to the print medium on the basis of the image datagenerated by the processing unit. Then, an image on which the achromaticareas have a high resolution can be printed with a high achromaticforming density, so a print image with a high resolution in theachromatic areas can be obtained.

The image processing method according to an aspect of the inventionincludes a step of reading a target to be read as the color data of Ncolors (N is a positive integer) that form a color space, a step ofgenerating pixel data of one pixel from the read color data of the Ncolors, a step of determining whether the generated pixel data ispresent in an achromatic edge area that includes an achromatic edge, anda step of generating, if the generated pixel data is determined to bepresent in the achromatic edge area, achromatic pixel data of the colorspace from one item of the read color data, for the pixels in theachromatic edge area, and also generating image data from the generatedachromatic pixel data.

As with the image processing apparatus described above, in theachromatic edge area in this image processing method, one item of colordata that has been read is used to generate achromatic pixel data forthe color space, so the color shift can be reduced. Since the one readcolor data item is the value of one pixel, a higher resolution can beobtained than when, for example, a plurality of color data items arehandled together to take the value of one pixel. Various forms of theabove image processing apparatus may be used in the image processingmethod. Steps that implement functions of the image processing apparatusmay be added.

The program according to an aspect of the invention causes one or morecomputers to execute the steps of the image processing method describedabove. The program may be stored on a storage medium that the computerscan read (such as a hard disk, ROM, FD, CD, and DVD). Alternatively, theprogram may be distributed from a computer to another through atransmission medium (the Internet, a LAN, or another communicationnetwork). Any other form may be used to transfer the program. When thisprogram is executed by a single computer or a plurality of computers,among which the steps of the program are shared, the steps of the imageprocessing method described above are executed, obtaining the sameeffect as the image processing method.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 schematically shows the structure of a printer according to anembodiment of the invention.

FIG. 2 is a flowchart illustrating an example of a read image datagenerating routine.

FIG. 3 illustrates processes of the read image data generating routine.

FIG. 4 illustrates generation of three-fold achromatic pixel data fromone color data item.

FIG. 5 illustrates an interpolation process performed on the data ofadjacent pixels to generate pixel data.

FIG. 6 illustrates a color CCD.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Next, an embodiment of the invention will be described with reference tothe drawings. FIG. 1 schematically shows the structure of a printer 20in the embodiment of the invention. The printer 20, which includes aprinting section 30 and a scanner 40 as shown in FIG. 1, is structuredas a multi-function printer having a printer function, scanner function,and copy function. The printing section 30 expels inks used as coloringagents to recording paper S used as a print medium. The scanner 40 readsa manuscript M placed on a glass surface 48. The printer 20 alsoincludes a main controller 21 that controls the printer 20 overall. Inthe printer 20, the main controller 21, printing section 30, and scanner40 are electrically interconnected through a bus 29.

The main controller 21 is structured as a microprocessor, the maincomponent of which is a CPU 22. The main controller 21 further includesa flash ROM 23, in which various types of processing programs are storedand data can be rewritten, as well as a RAM 24, in which data istemporarily stored and data is saved. The main controller 21 controlsthe printing section 30 so as to execute a print process and alsocontrols the scanner 40 so as to execute an image reading process.

The printing section 30 includes a print head 32 provided on the bottomsurface of a carriage supported so as to be movable in a horizontaldirection of the main body, a transfer mechanism 36 that transfers therecording paper S in the transfer direction, and ink cartridges (notshown) that hold inks, the inks being supplied from the ink cartridgesto the print head 32 through ink tubes. A plurality of nozzles 33, fromwhich cyan (C), magenta (M), yellow (Y), and black (K) inks areexpelled, are provided on the bottom surface of the print head 32. Thenozzles 33 and their nozzle strings 34 are generic names for thesecolors. The nozzle and nozzle string for cyan will be referred to belowas a nozzle 33C and a nozzle string 34C. The nozzle and nozzle stringfor magenta will be referred to below as a nozzle 33M and a nozzlestring 34M. The nozzle and nozzle string for yellow will be referred tobelow as a nozzle 33Y and a nozzle string 34Y. The nozzle and nozzlestring for black will be referred to below as a nozzle 33K and a nozzlestring 34K. With the printer 20, more nozzles 33K in black, which isachromatic, are provided than the monochromatic nozzles 33C, 33M, and33Y. That is, these nozzles are arranged so that the print density ofthe achromatic black ink is higher than the print density of thechromatic inks. In this embodiment, the resolution of the nozzles 33C,33M, and 33Y is 300 dpi, and the resolution of the nozzle 33K is 600dpi. The print head 32 expels the inks from the nozzles 33 by a methodin which a voltage is applied to a piezoelectric device to deform it andthereby pressurize the pertinent ink. The mechanism that applies apressure to the inks may use bubbles generated by heat from a heater.The transfer mechanism 36 includes a paper feeding roller disposed neara place from which the recording paper S is supplied, and also includesa transfer roller disposed near a place from which the recording paper Sis ejected.

The scanner 40 includes a contact image sensor (CIS) unit 41 that readsan image formed on the manuscript M placed on the glass surface 48, adrive roller 45 that moves the CIS unit 41 in the sub-scanning directionthrough a belt 46, and a control unit 51 that controls the scanner 40.The CIS unit 41 includes imaging devices 42 that read an image byreceiving light reflected on the manuscript M, a CCD 43 that receivescharges from the imaging devices 42 and transfers the received chargesto the control unit 51, and a light source 44 that emits light to themanuscript M. The imaging devices 42 are opto-electric conversiondevices that are arranged in the main scanning direction and correspondto pixels. When exposed to light, the imaging devices 42 convert thelight to charges and store the converted charges. The light source 44internally has a red LED 44R that lights in red, a green LED 44G thatlights in green, and a blue LED 44B that lights in blue. The lightsource 44 is structured so that light from any of these LEDs can bedirected the manuscript M. The CIS unit 41 moves in the sub-scanningdirection as the belt 46 is driven by the drive roller 45. The CCD imagesensor is just an example; a CMOS image sensor may be used instead. Thecontrol unit 51 has an emission control section 52 that controls lightemission from the light source 44, a CCD controller 53 that controls thedriving of the CCD 43, a timing generator (TG) 54 that outputs starttiming signals for various operations of the CIS unit 41 and othersignals, an analog front end (AFE) 55 that converts an electric signalreceived from the CIS unit 41 to a digital signal, and an imageprocessing section 56 that performs a prescribed process on the signalreceived from the AFE 55 to generate digital image data. The emissioncontrol section 52 outputs a lighting signal and other signals to thelight source 44. The CCD controller 53 generates a drive clockequivalent to a read timing signal, which is generated on the basis of amain clock received from the main controller 21, and outputs thegenerated drive clock to the TG 54. The TG 54 generates drive pulses,for the CIS unit 41, by which the read resolution becomes 1200, 600, and300 dpi. The image processing section 56 has an achromatic edgeidentifying section 57 that identifies an achromatic edge area includingan achromatic edge, and also has a pixel processing section 58 thatgenerates pixel data on the basis of whether the area is an achromaticedge area and then generates image data from the generated pixel data.

Next, the operation of the printer 20 structured as described above inthis embodiment will be described, particularly when the manuscript Mplaced on the glass surface 48 is read. FIG. 2 is a flowchartillustrating an example of a read image data generating routine executedby the CPU 22 in the main controller 21. This routine is stored in theflash ROM 23, and executed upon receipt of a high-speed, high-resolutioncopy command from an operation panel (not shown). In a process mainlydescribed below, to read an image, the CIS unit 41 is moved in thesub-scanning direction at a relatively high speed, and the read imagewith a resolution of 600 dpi by 200 dpi is expanded to an image with aresolution of 600 dpi by 600 dpi in the sub-scanning direction. When theroutine is executed, the CPU 22 causes the scanner 40 to read an image(step S100). In the process to read this image, a light beam isselected, one at a time, from light of three primary colors constitutinga color space, and the selected light beam is emitted from the lightsource 44 to the manuscript M. Then, the CIS unit 41 is moved in thesub-scanning direction to read the manuscript M. This process is aso-called line sequential process. The color space read by the scanner40 is an RGB color space. R values, G values, and B values are calledcolor data (denoted R value (255), for example), and pixel values, whichare RGB value, are called pixel data (denoted RGB values (255, 255,255), for example). The emission control section 52 selects a light beamone at a time from the light source 44 in emission control. The TG 54sets a timing at which charges are accumulated in the imaging devices42. The CCD controller 53 reads charges accumulated in the imagingdevices 42. The AFE 55 amplifies the charges and outputs the amplifiedcharges to the image processing section 56. The read result obtained inthis line sequential process is such that color data of the same type (Rvalues, for example) is linearly arranged in the main scanning directionand color data of different types linearly alternates. In thisembodiment, three color data items (R value, G value, and B value)adjacent in the sub-scanning direction in the obtained read result arecombined together to generate pixel data (RGB values) of one pixel.

After the image reading process has been executed and a prescribedamount of pixel data has been accumulated, the CPU 22 executes an areaexpansion process (step S110). FIG. 3 illustrates processes of the readimage data generating routine. In this area expansion process, an areaone pixel outside the pixels at the outermost circumference of the readresult is filled with pixels of the same type as the pixels at theoutermost circumference so that an achromatic edge area identificationprocess and the like can be executed for the pixels at the outermostcircumference of the read result (see the upper figure in FIG. 3). Theprescribed amount of pixel data may be, for example, pixel data in threerows so that the edge identification process can be executed.

Next, the CPU 22 executes the achromatic edge area identificationprocess (steps S120 to S160). In this process, the achromatic edgeidentifying section 57 identifies an achromatic edge area that includesan achromatic edge. The CPU 22 first sets pixels P (x, y) of interestthat are used to determine whether there is an edge and whether a pixelis achromatic (step S120). In this embodiment, pixels of interest areset sequentially to the right, starting from the left end of the top rowof the read data. Other pixels of interest are then set sequentiallyfrom the left end one row below the previous row to the right. Finally,pixels of interest are set up to the right end on the last row. Uponcompletion of setting the pixels of interest, the CPU 22 converts thepixel data P (x, y) to brightness data Y (x, y) including brightnessvalues (step S130, see the upper figure in FIG. 3). In this embodiment,the RGB color space is converted to a YCC color space.

The CPU 22 then calculates a Sobel value (P) (step S140). In thisembodiment, a Sobel filter V (P) in the vertical direction and a Sobelfilter H (P) in a horizontal direction are used to calculate the Sobelvalue (P) from the eight pixels adjacent to a pixel of interest (see thefigure in the middle in FIG. 3). The CPU 22 then calculates a Diff value(P) (step S150), which is a difference among RGB values used todetermine whether the pixel of interest is achromatic. The Diff value(P) can be obtained as the difference between the maximum and minimumRGB values of the pixel of interest. If the pixel of interest has RGBvalues (255, 210, 180), for example, then Diff (P) is determined to be75 by subtracting 180 from 255. The CPU 22 uses the obtained Sobel value(P) and Diff value (P) to determine whether the pixel P (x, y) ofinterest is present in the achromatic edge area (step S160). In thisembodiment, if the Sobel value (P) is equal to or greater than athreshold Thsobel, which has been experimentally determined, and theDiff value (P) is equal to or less than a threshold Thdiff, which hasalso been experimentally determined, then the pixel P (x, y) of interestis determined to be present in the achromatic edge area. The thresholdThsobel may be experimentally determined to be a value that can identifyan edge area, for example. The threshold Thdiff may be experimentallydetermined to be a value (80, for example) that is allowed as beingachromatic.

The CPU 22 then executes a pixel data generation process, which expandspixel data on the basis of whether the pixel of interest is present inan achromatic edge area (steps S170 and S180). In this process, thepixel processing section 58 uses one color data item read in the linesequential process to generate three-fold achromatic edge area in thesub-scanning direction as the values of the three primary colors of theRGB color space. In a non-achromatic edge area, the pixel processingsection 58 performs interpolation and generates three-fold pixels in thesub-scanning direction. First, in step S160, if the pixel P (x, y) ofinterest is not in an achromatic area, the CPU 22 uses the data of thepixels adjacent to the pixel of interest in the sub-scanning directionto generate three-fold pixel data in the sub-scanning direction throughan interpolation process (step S170). In this embodiment, the center ofthe three generated pixels has the RGB values of the pixel P (x, y) ofinterest, and the other generated pixels have pixel data that has beengenerated by performing interpolation on the data of the adjacentpixels. Interpolation processes include nearest neighbor interpolation,bilinear interpolation, and bicubic interpolation. Of theseinterpolation processes, bilinear interpolation and bicubicinterpolation are preferable, so bilinear interpolation is performed inthis embodiment. If the pixel P (x, y) of interest is present in theachromatic edge area in step S160, the CPU 22 uses one read color dataitem to generate three-fold achromatic pixel data in the sub-scanningdirection, on the basis of the positions of the color data read by theCIS unit 41, as the values of the three primary colors of the RGB colorspace (step S180). For example, to generate the pixel data in step S100,emissions from the light source 44 were controlled in the order of R, G,B in the sub-scanning direction and a read operation was performed whilethe CIS unit 41 were being moved. If the pixel of interest is present inan edge area and is achromatic, achromatic pixel data items generatedfrom the individual read color data items more accurately reflect themanuscript M than when one pixel data item is generated by combining theindividual read color data items together. In this embodiment, in thesub-scanning direction, an R value is used as G and B values to generatepixel data (R, R, R). For the next pixel, a G value is used as R and Bvalues to generate pixel data (G, G, G). For the further next pixel, a Bvalue is used as R and G values to generate pixel data (B, B, B).

Now, the pixel data generation process in steps S170 and S180 will bedescribed by using a specific example. FIG. 4 illustrates generation ofthree-fold achromatic pixel data from one read color data item. FIG. 5illustrates an interpolation process performed on the data of adjacentpixels to generate three-fold pixel data. As shown in FIGS. 4 and 5,when R value (255), G value (210), and B value (180) are read as colordata, the process in step S100 produces RGB values (255, 210, 180) asthe pixel data of the pixel of interest. When, for example, the pixel ofinterest is present in an achromatic edge area and a portion including aboundary between white and block areas is read as shown in FIG. 5,pixels that were originally present in the achromatic edge area becomenon-achromatic pixels, the pixel of interest itself may cause a colorshift. Accordingly, when an interpolation process is performed on thepixel of interest, the generated pixels also cause a color shift (seethe lower figure in FIG. 5). With the printer 20 in this embodiment,however, when the pixel of interest is present in an achromatic edgearea as shown in FIG. 4, achromatic RGB values (255, 255, 255), (210,210, 210), and (180, 180, 180) are respectively generated from the Rvalue, G value, and B value on the basis of the read positions in thesub-scanning direction (see the lower figure in FIG. 3 and the lowerfigure in FIG. 4). As described above, since actually read values areused without alteration to generate three pixels, the resolution can beincreased. Furthermore, since the three pixels are achromatic pixels,their color shift can be suppressed. Even when an interpolation processis performed on pixels in other than the achromatic edge area, includingachromatic pixels, to generate three-fold pixel data, a color shift doesnot easily occur and a problem is less likely to occur. Pixel data inthe achromatic edge area is expanded in this way.

After the pixel data has been generated in steps S170 and S180, the CPU22 determines whether the achromatic edge area identification processand pixel data generation process have been performed on all pixel datain the read result (step S190). If these processes have not beenterminated for all the pixel data, the processes in step S120 and laterdescribed above are repeated. That is, the next pixel of interest is setand the achromatic edge area identification process and pixel datageneration process are executed on the set pixel of interest. If theseprocesses have been terminated for all the pixel data, image data isgenerated by using the generated pixel data as pixel values. Thegenerated image data is output to the printing section 30 (step S200),terminating the routines. Upon receipt of the image data, the printingsection 30 executes a print process. In the print process, the CPU 22 inthe printer 20 drives the transfer mechanism 36 to transfer therecording paper S, and controls the print head 32 so that it expels inkson the recording paper S on the basis of the image data. Since the readimage data has a reduced color shift in the achromatic edge area and athree-fold resolution in the sub-scanning direction, the printingcapacity of the print head 32, in which the print density of the blackink is increased, can be adequately derived, and thereby a superiorprint result can be obtained.

The relationship between the components in the embodiment of theinvention and the components in aspects of the invention will beclarified. The CIS unit 41 in the embodiment corresponds to the readingunit in the aspects of the invention, the main controller 21 andachromatic edge identifying section 57 in the embodiment correspond tothe identifying unit in the aspects of the invention, the maincontroller 21 and pixel processing section 58 in the embodimentcorrespond to the processing unit in the aspects of the invention, theprinting section 30 in the embodiment corresponds to the printer in theaspects of the invention, and the main controller 21 in the embodimentcorresponds to the print controller in the aspects of the invention. Themanuscript M in the embodiment corresponds to the target to be read inthe aspects of the invention, the inks in the embodiment correspond tothe coloring agents in the aspects of the invention, and the recordingpaper S corresponds to the print medium in the aspects of the invention.In the embodiment, an example of the image processing method in anaspect of the invention is clarified by explaining the operation of theprinter 20.

The printer 20 in the embodiment, which has been described in detail,reads the manuscript M by handing a plurality of pixels as the colordata of an RGB color space of three primary colors, and identifies anachromatic edge area in the read area. The printer 20 then uses one readcolor data item to generate achromatic pixel data of the RGB color spacefor the pixels in the identified achromatic edge area, and alsogenerates image data from the generated achromatic pixel data. Asdescribed above, in the achromatic edge area, one item of color datathat has been read is used to generate achromatic pixel data for thecolor space, so it is possible to reduce a color shift of the type thatis caused when the pixel data of one pixel is generated from a pluralityof adjacent color data items. Since the one read color data item is thevalue of one pixel, a higher resolution can be obtained than when, forexample, a plurality of color data items are handled together to takethe value of one pixel.

When pixel data of one pixel is generated from the color data of threeadjacent colors in the read color data, the generated pixel data may bepresent in an achromatic edge area. Then, image data is generated byusing the color data of the three colors included in the pixel datagenerated on the basis of the positions of the color data read by theCIS unit 41 as the achromatic pixel data of the three pixels.Accordingly, the resolution can be relatively easily increased to threetimes. Furthermore, since the achromatic edge area is identified on thebasis of brightness information obtained from the pixel data of onepixel that have been generated from the color data of three adjacentcolors in the read color data. Accordingly, the achromatic edge area canbe easily identified and the resolution can also be easily increased.Furthermore, since whether the pixel is achromatic is determined on thebasis of differences among color data values included in the pixel dataof one pixel, which has been generated from the color data of theadjacent three colors in the read color data, an achromatic area can beidentified by a relatively simple process. The color data of the pixelsadjacent to a pixel in other than the achromatic edge area is also usedto generate data of three pixels through an interpolation process, sothe resolution of the entire image data can be increased by use of theinterpolation process. The CIS unit 41 has the imaging devices 42, whichare opto-electric conversion devices, arranged in the main scanningdirection. The CIS unit 41 selects a light beam, one at a time, from thelight beams of the three colors constituting the RGB color space,directs the selected light beam to the manuscript M, moves theopto-electric conversion devices in the sub-scanning direction, andreads the manuscript M. Accordingly, the resolution can also beincreased in the sub-scanning direction by increasing the moving speedof the CIS unit 41 in the sub-scanning direction. Both a fast read speedand a high resolution are thereby achieved. Furthermore, the print head32 of the printing section 30 includes more nozzle strings 34 of theachromatic ink than nozzle strings of the monochromatic inks, that is,the print density of the achromatic black ink is higher than the printdensity of the chromatic inks. Therefore, an image having a highresolution in the achromatic area can be used to achieve printing with ahigh achromatic print density and thereby a printed image having a highresolution in the achromatic area can be obtained.

The embodiment of the invention described above is not a limitation. Itwill be appreciated that various aspects are possible without departingfrom the technical scope of the embodiment of the invention.

For example, in the embodiment described above, the pixel data of onepixel has been generated from the color data of three adjacent colors inthe read color data, and the generated pixel data has been used forbrightness conversion to identify an edge area. However, this is not alimitation if an edge area can be identified. It may not be necessary togenerate the pixel data of one pixel from the color data of threeadjacent colors or to perform brightness conversion. In addition,although an achromatic area has been identified on the basis ofdifferences among the color data values of the pixel data of one pixelgenerated from the color data of three adjacent colors in the read colordata, this is not a limitation if an achromatic edge area can beidentified. It may not be necessary to generate pixel data of one pixelfrom the color data of the three adjacent colors or calculate thedifferences among the color data values. Any method can be used withoutany restrictions if it can identify an achromatic edge area.

In the embodiment described above, a Sobel value (P) and a Diff value(P) have been used to identify an achromatic edge area in step S160.However, another condition may be substituted for or added to thesevalues. For example, a condition may be used to determine whether thereare white and black areas around a pixel of interest (around eight byeight pixels, for examples). Although the manuscript M and the readresult have not been described in the above embodiment, the areasadjacent to the achromatic edge area are preferably white in color.Then, an achromatic edge area can be easily identified and a color shiftis less likely to occur.

Although pixel data to be read has been values of an RGB color space,this is not a limitation. The values of a CMY(K) color space may be usedinstead, for example.

In the embodiment described above, the manuscript M has been read with aresolution of 600 dpi by 200 dpi and the resolution has been increasedto 600 dpi by 600 dpi. However, this is not a limitation. For example,the manuscript M may be read with a resolution of 600 dpi by 300 dpi,the resolution may then be increased to three times in the sub-scanningdirection, that is, to 600 dpi by 900 dpi, after which the resolutionmay be reduced to 600 dpi by 600 dpi. In this case as well, the sameeffect as in the above embodiment can be obtained. When an image isread, it is more preferable to shorten the read time by increasing themoving speed of the CIS unit 41 than to read the image with a resolutionof 600 dpi by 600 dpi.

In the embodiment described above, linear read results of the RGB colorshave been obtained by use of the CIS unit 41. However, this is not alimitation if pixels can be read by use of a plurality of primary colorsin a prescribed color space. For example, the read unit used may emitwhite light to the manuscript M and may have a plurality of imagingdevices, each of which can read one color of RGB. FIG. 6 illustrates thecolor CCD 41B. A color filter, in which a window of 2 pixels by 2 pixelsis used as a unit, is placed on the CCD 41B and imaging devices. Eachwindow has one R color and one B color on a diagonal line and also hastwo G colors on the opposite diagonal line. Each pixel can recognize anyone of the R, G, and B colors. In this case, the pixel data can beexpanded horizontally and vertically to increase the resolution. The useof this type of read unit also achieves a reduced color shift and highresolution.

In the embodiment described above, the multi-function printer, which canexecute printing, scanning, and copying, has been described as the imageprocessing apparatus according to the embodiment of the invention.However, the image processing apparatus may be a scanner alone or FAXmachine. Although the processing in the above embodiment has beenprocessing during copying, the processing may be processing executedwhile an image is read or during a FAX transmission. Although thescanner 40 has been of the flatbed type, in which the manuscript M issecured and the CIS unit 41 is moved to read the image, a type in whichthe CIS unit 41 is secured and the manuscript M is moved to read theimage may be used instead. Although the printing section 30 has been ofthe inkjet type, an electrophotographic laser printer, a thermaltransfer printer, or a dot impact printer may be used instead. Althoughthe embodiment of the invention has been described with an aspect of theprinter 20, an aspect of the image processing method or an aspect of aprogram thereof may be used instead.

The embodiment of the invention can be used in industries related toimage processing.

The entire disclosure of Japanese Patent Application Nos. 2010-7760,filed Jan. 18, 2010 are expressly incorporated by reference herein.

1. An image processing apparatus comprising: a read unit that reads atarget to be read as color data of N colors (N is a positive integer)that form a color space; a generator that generates pixel data of onepixel from the read color data of the N colors; a determining unit thatdetermines whether the generated pixel data is present in an achromaticedge area that includes an achromatic edge; and a processing unit that,if the generated pixel data is determined to be present in theachromatic edge area, generates, for pixels in the achromatic edge area,achromatic pixel data of the color space from one item of the read colordata of the N colors forming the color space and also generates imagedata from the generated achromatic pixel data.
 2. The image processingapparatus according to claim 1, wherein if the generated pixel data isdetermined to be present in the achromatic edge area, color data of Ncolors included in the pixel data, which has been generated on the basisof positions of the color data read by the read unit, is used asachromatic pixel data of N pixels to generate the image data.
 3. Theimage processing apparatus according to claim 1, further comprising anidentifying unit that identifies the achromatic edge area on the basisof brightness information obtained from the generated pixel data.
 4. Theimage processing apparatus according to claim 1, wherein the processingunit also uses color data of pixels adjacent to a pixel in an area otherthan the achromatic edge area to generate pixel data of the color spacethrough an interpolation process, and uses the generated pixel data togenerate image data.
 5. The image processing apparatus according toclaim 1, wherein: the read unit has opto-electric conversion devices,arranged in a main scanning direction, which opto-electrically convertlight obtained through the target to be read; the read unit selects alight beam, one at a time, from N-color light beams constituting thecolor space and directs the selected light beam to the target; and theread unit moves in a sub-scanning direction and reads the target.
 6. Theimage processing apparatus according to claim 1, further comprising: aprinter that has an achromatic coloring agent and a chromatic coloringagent, the achromatic coloring agent having a higher forming density ona print medium than the chromatic coloring agent; and a print controllerthat controls the printer so that the coloring agents are transferred tothe print medium; wherein the print controller controls the printer sothat the coloring agents are transferred to the print medium on thebasis of the image data generated by the processing unit.
 7. An imageprocessing method, comprising: reading a target to be read as color dataof N colors (N is a positive integer) that form a color space;generating pixel data of one pixel from the read color data of the Ncolors; determining whether the generated pixel data is present in anachromatic edge area that includes an achromatic edge, and generating,if the generated pixel data is determined to be present in theachromatic edge area, achromatic pixel data of the color space from oneitem of the read color data, for pixels in the achromatic edge area, andalso generating image data from the generated achromatic pixel data. 8.A storage medium causing one or more computers to execute the steps ofthe image processing method of claim 7.